Linux Kernel up to 6.18.7 slab kmalloc_nolock privilege escalation

Summaryinfo

A vulnerability labeled as critical has been found in Linux Kernel up to 6.18.7. The impacted element is the function kmalloc_nolock of the component slab. Such manipulation leads to an unknown weakness. This vulnerability is traded as CVE-2026-23134. There is no exploit available. The affected component should be upgraded.

Detailsinfo

A vulnerability, which was classified as critical, has been found in Linux Kernel up to 6.18.7. Affected by this issue is the function kmalloc_nolock of the component slab. The impact remains unknown. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: slab: fix kmalloc_nolock() context check for PREEMPT_RT On PREEMPT_RT kernels, local_lock becomes a sleeping lock. The current check in kmalloc_nolock() only verifies we're not in NMI or hard IRQ context, but misses the case where preemption is disabled. When a BPF program runs from a tracepoint with preemption disabled (preempt_count > 0), kmalloc_nolock() proceeds to call local_lock_irqsave() which attempts to acquire a sleeping lock, triggering: BUG: sleeping function called from invalid context in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 6128 preempt_count: 2, expected: 0 Fix this by checking !preemptible() on PREEMPT_RT, which directly expresses the constraint that we cannot take a sleeping lock when preemption is disabled. This encompasses the previous checks for NMI and hard IRQ contexts while also catching cases where preemption is disabled.

The advisory is available at git.kernel.org. This vulnerability is handled as CVE-2026-23134 since 01/13/2026. The exploitation is known to be difficult. Technical details are known, but there is no available exploit. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 03/18/2026).

The vulnerability scanner Nessus provides a plugin with the ID 299326 (Linux Distros Unpatched Vulnerability : CVE-2026-23134), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.18.8 eliminates this vulnerability. Applying the patch f60ba4a97ae3f94e4818722ed2e4d260bbb17b44/99a3e3a1cfc93b8fe318c0a3a5cfb01f1d4ad53c is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at Tenable (299326). If you want to get best quality of vulnerability data, you may have to visit VulDB.

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.18.0
• 6.18.1
• 6.18.2
• 6.18.3
• 6.18.4
• 6.18.5
• 6.18.6
• 6.18.7

License

• open-source

Website

• Vendor: https://www.kernel.org/

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If you want to get best quality of vulnerability data, you may have to visit VulDB.

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